In general, the measurement of particles existing in a clean space, such as a clean room for a process of producing a semiconductor, is a very important factor for the process of producing the semiconductor, and a technology capable of measuring even a nanoscale particle is required as a line width of the semiconductor is decreased in accordance with the development of the semiconductor technology. In addition, recently, as a technology using particles with nanometer to micrometer-sized structures has been developed, a technology, which not only measures ultrafine particles but also classifies the particles according to the size, is considered as a basic condition for researches.
As such, a need for technologies for measuring, evaluating, and classifying the particles is increased in various fields, and recently, the development is being actively conducted on an electrical particle classifying apparatus (different mobility analyzer (DMA)) which classifies the particles based on a difference in mobility of the particles caused by electrostatic force.
In this case, a typical DMA is configured to use a method of scanning voltage in order to measure the distribution of sizes of particles in an aerosol, and a scanning time of about two minutes is generally required, such that a large amount of time is required to classify the particles. In the case of researches on emission of air pollutants, particularly, soot and smoke produced by a diesel engine, it is nearly impossible to measure emission characteristics of the soot and smoke by using the existing DMA because sizes and concentration of the soot and smoke often vary in a very short period of time. A multi-system for classifying particles (multi-stage differential mobility analyzer (MDMA)) has been proposed as an alternative for the DMA. The MDMA includes a cylindrical high-voltage electrode installed in an aerosol flow direction, and several ports (ring electrodes) adjacent to the cylindrical high-voltage electrode, and the MDMA is configured to capture a particle having a comparatively small size at an initial part of an aerosol flow path, and capture a particle having a comparatively large size at a rear end of the aerosol flow path, thereby reducing the scanning time.
However, the MDMA has a drawback in that a very long length of the aerosol flow path needs to be ensured in order to capture even the particle having a large size, and as a result, an overall size of the apparatus is greatly increased, which leads to inefficiency. A method of increasing applied voltage has been proposed to solve the aforementioned problem, but this method has a problem in that reliability in classifying the particles deteriorates because the particle having a large size may also be captured at the initial part of the aerosol flow path when the applied voltage is high.
In addition, the MDMA measures a charge amount of the particle attached to the port in order to recognize the sizes or the distribution of the particles, but there is a problem in that the charge amount is not accurately measured in a case in which the charge amount of the particle is small, and as a result, it is impossible to measure the distribution of the particles, and particularly, it is impossible to accurately measure the number of particles to be classified.
As a method of measuring the number of particles, there is a method of condensing a liquid around the particle by using the particle as a condensation nucleus, growing the particle to make a large particle, and then optically counting the number of particles one by one. However, in the related art, a condensation nucleus counter (condensation particle counter (CPC)) is used by being connected to the MDMA or a particle classifier in order to measure the number of particles discharged from the MDMA or the particle classifier, and the particles discharged from the particle classifier pass through both a saturator and a condenser that constitute the condensation nucleus counter, and then the particles are measured as the particles reach a detector (or an optical device). In use of this configuration, the particles remain in the condensation nucleus counter over a very long period of time, and as a result, there is a problem in that a reaction time of the system is significantly increased.
In addition, the saturator and the condenser need to be separately configured for each size of the aerosol particle, and as a result, there is a problem in that a configuration of the system is complicated.